This section is from "The Horticulturist, And Journal Of Rural Art And Rural Taste", by P. Barry, A. J. Downing, J. Jay Smith, Peter B. Mead, F. W. Woodward, Henry T. Williams. Also available from Amazon: Horticulturist and Journal of Rural Art and Rural Taste.
The ground is almost alive with the common earth-worm. Wherever mould is turned up, there these sappers and miners are turned up with it. They are nature's ploughmen. They bore the stubborn soil in every direction, and render it pervious to air, rain, and the fibres of plants. Without these auxiliaries, "the farmer," says Gilbert White, "would find that his land would become cold, hard-boned and sterile." The green mantle of vegetation which covers the earth is dependent upon the worms which burrow in the bowels of it. What conveys a more definite idea of the magnitude of their operations, they are perpetually replenishing the upper soil, and covering with soft and fine material a crust which before was close and ungenial. They swallow a quantity of earth with their food, and having extracted the nutriment they eject the remainder at the outlet of their holes. This refuse forms the worm-crusts which are the annoyance of the gardener, who might be reconciled to them if he were aware that the depositors save him a hundred times more labor than they cause. They play a most important part in the economy of vegetation, and we see why they teem throughout the surface of the globe.
Mr. Charles Darwin has shown that in thirteen years a field of pasture was covered to a depth of three inches and a half with the mould discharged from their intestines, and in another case the layer they had accumulated in eighty years was from twelve to fourteen inches thick. - Quarterly Review.